1. Field of the Invention
The present invention relates to a power transmission chain of the inverted tooth type, commonly referred to as a "silent chain". The silent chain is utilized as a driving force transmitting apparatus in which a wrapping and meshing transmission is effected by use of an endless chain.
2. Description of the Prior Art
A silent chain is generally constructed, as illustrated in FIG. 1, by connecting, in endless fashion, a plurality of link plates L by means of connecting pins P. Each of the link plates L has teeth which are adapted to mesh with a sprocket S and also has a pair of connecting pin insertion holes H.
The configurations of the connecting pins are divided broadly into (1) a rocker-joint type connecting pin means consisting of a seat pin and a rocker pin and (2) a round pin type connecting pin of circular cross section. The rocker-joint type connecting pin (hereinafter referred to merely as a connecting pin) is more commonly employed in silent chains.
The present invention relates to a silent chain in which the link plates are connected by the connecting pins such as, for example, a silent chain connected by the connecting pins as disclosed in the Official Gazette of Laid-open Japanese patent application No. 62-101940 (1987) As shown in FIG. 3, a traction load-transmitting, side, inner surface H' of a connecting pin insertion hole H provided on a toothed link plate L is formed in the shape of a convex surface protruding toward the inside of the insertion hole H so that the seat pin P' can be prevented from being rotated by virtue of the convex surface.
That is, the connecting pin insertion hole is designed so as not to cause mutual slippage on the connecting surface between the insertion hole H and the seat pin P', when the link plate L is meshed with the sprocket and is bent around the sprocket in accordance with the rotation of the sprocket, in order to achieve a rolling contact at the mutually contacting back surfaces between the seat pin and the rocker pin.
In the above-described prior art, since the connecting pin insertion hole is formed with a convex surface, which is provided for preventing rotational displacement, there is formed a rotation stopping corner portion D which is nonlinearly formed at the connecting point or junction of the concave surface and the convex surface formed on the inner periphery of the insertion hole. As a result, there is caused the problem that a crack is likely to be generated in the link plate, said crack extending from the rotation stopping corner portion D, due to the application of the load acting for preventing the mutual rotation which concentrates force on the rotation stopping corner portion D. Such cracking can result in a breaking of the link plate.